Conventionally, an image forming apparatus such as a copying machine, a printer, and a facsimile machine, and an image reading apparatus, each include a sheet conveying apparatus for reversing a sheet, such as recording paper and a document, and reconveying the reversed sheet to an image forming portion and an image reading portion. For example, in the image forming apparatus including the sheet conveying apparatus, after the image forming portion forms an image on one side (first side) of the sheet, the sheet conveying apparatus reconveys the sheet to the image forming portion, and the image forming portion forms an image on the other side (second side) of the sheet.
As the sheet conveying apparatus, there is a sheet conveying apparatus including forward and reverse rotatable sheet discharging rollers, which perform forward and reverse rotation at the time of forming an image on the second side of the sheet, to thereby convey the sheet to a reconveying passage while switching back the sheet (see PTL 1). However, in the case of this structure, the succeeding sheet cannot reach the sheet discharging roller pair until the preceding sheet that is being reversed exits the sheet discharging rollers completely and the rotation direction of the sheet discharging roller pair is switched to a normal direction. Therefore, at the time of successive printing, large sheet intervals need to be ensured, resulting in lower productivity.
In view of the above, in order to enhance the productivity, as an automatic document feeder serving as the sheet conveying apparatus which is provided in, for example, the image reading apparatus to convey a document to the image reading portion, there is an automatic document feeder capable of separating a driven rotatable member that is brought into pressure contact with a sheet reversing roller to convey the document (see PTL 2). After the preceding sheet (document) reversed by the sheet reversing roller reaches an intermediate roller arranged downstream of the sheet reversing roller in a sheet reversing direction, the driven rotatable member is separated, and therefore the preceding sheet and the succeeding sheet are conveyed to pass each other by the sheet reversing roller. As a result, the productivity is enhanced. Note that, as the structure in which the two sheets are conveyed to pass each other, there is a structure in which the sheet reversing roller is provided with a torque limiter, to thereby enhance the productivity without separating the sheet reversing roller (see PTL 3). However, in the structures of PTL 2 and PTL 3, the edge (leading edge) of the succeeding sheet traveling toward the sheet reversing roller is brought into contact with the surface of the preceding sheet that is being conveyed away from the sheet reversing roller. In this case, the edge of the succeeding sheet may damage the surface of the preceding sheet. Note that, in a case of the sheet having an image formed thereon, the damage to the surface of the sheet refers to degradation in quality of the image thus formed, and in a case where the sheet to be conveyed is a document, the damage to the surface of the sheet refers to degradation in quality of the document surface due to slide contact with the edge of the sheet. Further, the damage to the surface of the sheet is significant due to the fact that the moving direction of the surface of the preceding sheet and the moving direction of the edge of the succeeding sheet pass each other.